The present invention relates to a diagnosis system for a motor vehicle.
Recently, a motor vehicle has been equipped with an electronic control system for controlling various components of an engine, such as fuel injectors, thereby improving driveability, exhaust gas emission, fuel consumption, and engine power. The electronic control system controls the components based on information represented by output signals from various sensors for detecting engine operating conditions. Accordingly, if malfunctions of components and sensors occur, the engine does not properly operate.
However, because of the complexity of the electronic control system, it is difficult to immediately find out the trouble. Accordingly, a trouble diagnosis device for easily checking the electronic control system should be equipment in an auto shop.
Japanese patent application Laid-Open No. 58-12848 discloses a diagnosis system in which an exclusive checking device is provided for measuring a pulse duration of fuel injection and an engine speed, and for checking whether idling speed is normal. The checking device is provided for diagnosing only designated specific types of motor vehicle.
However, programs and communication systems of the electronic control systems differ with types of electronic control systems. For example, there are various communication systems such as the start-stop system, clock synchronization and others. Further, the signaling speed also differ in types of communication systems.
In order to diagnose various vehicles, it is necessary to equip several types of checking devices corresponding to respective types of electronic control systems, which is inconvenient in management and is uneconomical.
Further, a diagnosis system which stores a plurality of programs and communication systems for diagnosing various types of electronic control systems has been proposed. In such a system, a code representing a type of an electronic control system equipped in a vehicle to be diagnosed must be inputted in the diagnosis system for selecting the program and the communication system. However, it is troublesome work to confirm the corresponding code and to input the code consisting of a plurality of figures. If a mis-code is input, a correct program and communication system are not selected, so that a proper diagnosis can not be performed.